Graham Lochead 01/02/10 Autoionization of strontium Rydberg states.

Graham Lochead01/02/10

Autoionization of strontium Rydberg states

Graham Lochead01/02/10

Outline

• Autoionization/experimental overview

• Low n results

• High n results

Graham Lochead01/02/10

Autoionization

5s2 5s5p 5sns(d) 5pns(d) 5s1/2

461 nmprobe

413/420 nmcoupling

408 nmautoionization

4 μs overlappedcounterpropagating CW10 ns pulse

Prepare atomsin ground state

Graham Lochead01/02/10

Data acquisition

Step the Rydberg coupling laser over the transition

Collect and integrate the ion signal at each wavelength

Fit a Gaussian to the lineshape

Extract height and normalise by atom number/pulse energy where appropriate

Graham Lochead01/02/10

Error analysis

Analysis not yet completed

Major sources of error:• Atom number fluctuation• Shot-to-shot fluctuation of the pulse laser power

Initial estimates of signal error < 15%

Graham Lochead01/02/10

20S Rydberg state lifetime

Graham Lochead01/02/10

20S autoionizing spectrum

Graham Lochead01/02/10

19D Rydberg state lifetime

Graham Lochead01/02/10

19D Rydberg state lifetime

Lifetime previously measured to be 740 ± 40 ns

Grafström et. al, PRA 27, 947 (1983)

Graham Lochead01/02/10

19D autoionizing spcetrum

Shape due to quantum defect difference

Cooke et. al, PRL 40, 178 (1977)

Graham Lochead01/02/10

Total Rydberg ionization

• Were able to completely ionize Rydbergs

• Loss fraction calculated – total Rydberg number

• Can calculate Rydberg-Rydberg ionization

Graham Lochead01/02/10

56D lifetime measurements

413 power (mW) Lifetime (μs)

5 16.3 ± 0.9

10 80 ± 6

15 98 ± 5

20 109 ± 19

Dutta et. al, PRL 86, 3993 (2001)

Possibly caused by high angular momentum state mixing

Graham Lochead01/02/10

56D autoionizing spectrum

Graham Lochead01/02/10

56D density effects

Graham Lochead01/02/10

Outlook

• Finish error analysis

• Follow up experiments without pulse laser

• Explain the 56D data